JPS6054908A - Extraction of soluble phosphate from natural phosphate of iron and aluminum by use of carbonate of alkali metal and hydroxide solution - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the extraction of soluble phosphate from naturally occurring iron and aluminum phosphates.

The prior art involves dissolving complex phosphates of iron and aluminum in mono-lithium hydroxide, as discussed in more detail below.

The present invention is characterized by the use of an alkali metal carbonate solution to leach the naturally occurring phosphoric acid Ju. In a preferred embodiment of the invention, following carbonate leaching,
It is further leached with alkali metal hydroxide. The method of the invention can be applied to Christmas Island, Senegal, Brazil.
naturally occurring J, including those from other sources.
It can be applied to many types of phosphates.

The carbonate leaching is preferably carried out at high temperature, for example from 70°C and at the boiling point at atmospheric pressure or from 100°C to 150°C under increased fF.

In one form of the invention, the naturally occurring iron and aluminum phosphate, balundite, is leached with a potassium carbonate solution under pressure at 100°C to 150°C.
Make a solution of potassium hephosphate and potassium aluminate. The remaining solids are further leached with potassium hydroxide solution at 70°C to 90°C to essentially completely extract the phosphorus and aluminum in the initial Valandai I. The remaining solids are separated from the solution and the solution is cooled to separate the potassium orthophosphate. The remaining solution is cooled to precipitate the aluminum trihydrate and the resulting potassium carbonate is further recycled to the balundite leaching.

In simplified form, the reaction that occurs is: 1.2"ePO4+3 to 2C03+3H20→2Fe(
OH) 3+2 to 3PO4+3CO22, 2AIPO+4
to 4CO3 1+2KA l 02+2 to 3PO4+4. GO,.

3, F e P O4+ 3 K Oto1→Fe(o
H) 10 to 3Po4 4, A I PO4+4KOH → KA I O2+ to 3 PO4+ 21-1205,
2KA I O+31-120+CO2→ K Co
-1-2A I (Oto1) 33 .

In another form of the invention, naturally occurring complex calcium-iron-aluminum phosphate chrysalis C-grade rock is leached with a hot solution of thorium carbonate and thorium or-1-phosphate. Make a solution of sodium aluminate. Hydroxylate residual solids.

Leaching with a hot solution of sodium brings into solution essentially all of the phosphorus and aluminum that was bound to the iron and aluminum in the original rock. The residual solids, which in terms of wood are calcium phosphate and iron hydroxide, are separated from the solution and then
The solution is cooled to 77 I and the sodium orthophosphate crystallizes out. The residual solution is carbonated to precipitate aluminum hydroxide and the resulting mono-lium carbonate solution is recycled to further leach Christmas Island C-grade rock.

In simplified form, the reaction that occurs is: 2FePO1000 3NaCo +3
3 → 2F (3 (01-1) 3+2N83P04+3CO
22A I PO4+4Na2Go3 -+2NaAlO+Na PO4+40023 Fe2
(01-1) 30 Na5PO.

-○ - A I PO4+-'lNaOH -+NaA 102+Na5P04-1-21-(20
2NaΔIQ2+CO,, +31-1. ．． 0-+Na
It is thought to be Co-1-2AI(OH)33.

In a third form of the invention, calcium phosphate rock, which is undesirable for conventional fertilizer production because it is contaminated with small amounts of iron and aluminum phosphates, is treated to reduce the iron and aluminum content to a low level. -ru. Low grade floc (rlorida) rocks are this type of rock. After leaching with a hot solution of sodium carbonate, the resulting sodium carbonate and phosphorus M#:A solution is separated from unreacted rock and iron hydroxide. By classifying the insoluble substances and removing as much colloidal iron hydroxide as possible, the product can be used for normal fertilizer production.

The solution of sodium phosphate and sodium aluminate is cooled to crystallize sodium orthophosphate, and the resulting solution is carbonated to produce sodium carbonate and aluminum hydroxide. Sodium carbonate is recycled to cover further leaching of low-grade Florida rock.

In a simplified form, the reaction that takes place can be considered as shown in the equation (outlined for the second embodiment of the invention).

In the detailed description of the invention, it should be clearly understood that where potassium compounds are mentioned, sodium compounds also apply and vice versa.

Advantages Prior art involves the dissolution of complex phosphates of iron and aluminum in sodium hydroxide. The resulting solution has no residual solids and upon cooling crystallizes the sthorium phosphate and decomposes the resulting sthorium aluminate solution to aluminum hydroxide and sthorium hydroxide.

Please see below. Rotl+bau
m) and Reeve, [Christmas Island C
Alumina and phosphate extraction from phosphate (neco
vcryOf＾Iumina and Phospha
te from ChristmasIsland C
Phosphate) J, Nico Zealand Journal of Science (N, Z, Journal
ofScience) Volume 11, Issue 4, December,
1968.

This technique has the distinct advantage that dissolved sodium combined with aluminum can be recovered as sodium hydroxide. However, the Bayer process, sodium aluminate decomposition, requires large decomposition vessels, recirculation of large volumes of seed aluminum hydroxide, and the use of relatively dilute solutions to accelerate the decomposition of sodium aluminate. It is. Bayer decomposition, NaAl0 +21-120 ==-" NaOH + AI (01-1>3 In order to reuse the recovered sodium hydroxide, it must be evaporated. From equation 2, the water reacting with the aluminum phosphate It will be seen that only 25% of the sodium oxide is recovered from the Bayer process and none from the iron phosphate (Equation 3).

91 The process of the present invention has the advantage that the investment and operating costs of large-scale peptizers, evaporators, and seed recirculation equipment are eliminated. The relatively small amount of alkali metal carbon MJiJ produced upon decomposition of the alkali metal aluminate is recycled to further dissolve the phosphate rock through reactions 1 and 2.

The invention further has the advantage that potassium carbonates and hydroxides can be used to produce valuable potassium phosphate. If potassium hydroxide is used to dissolve iron and aluminum phosphates, potassium aluminate is obtained.Potassium hydroxide is recovered in a method similar to the PiJt method using lithium aluminate. Potassium aluminate can be easily decomposed with carbon dioxide, although it is not suitable for this purpose.

The invention is further illustrated in the following non-limiting examples.

Example 1 100 g of balandite from Christmas Island were ground in a hot solution of 10 - thorium carbonate recycled from a previous experiment and leached for 1 hour at 70° C. in a stirred vessel. This dissolved approximately 13% of the phosphate present in the original rock.

The milled balundite slurry was further reacted with sodium hydroxide in a stirring vessel.

The sodium hydroxide was added as a 50% solution and the balundite suspension was stirred at 80° C. for 30 minutes. The amount of sodium hydroxide added is the amount present in the initial balundite [caustic available].
ble ) calculated to be stoichiometrically equivalent to J phosphate. A "causticizable" phosphate is defined as having an equivalent amount of total phosphorus @ jg less than 0.7 times the calcium present, eg, calcium phosphate.

The residual solids, consisting mostly of insoluble iron compounds and calcium phosphate, were filtered from the leach solution at 70°C. The clarified solution was then cooled to 20° C., in which case virtually all of the phosphorus salt present crystallized out as sodium orthophosphate.

filtering off the sodium orthophosphate and reheating the remaining sodium aluminate solution to 35°C;
And a small amount of aluminum hydroxide was added to promote the subsequent precipitation. Carbon dioxide was bubbled into the solution to suspend the water aluminum and decompose the sodium aluminate to 92F[tl sodium and aluminum hydroxide. 3 o'clock IF! l After carbonation,
The aluminum hydroxide is filtered at 35°C, and the resulting sodium carbonate solution is cooled to 20°C to crystallize and collect the sodium carbonate. The residual solution containing sodium carbonate and a small amount of lithium phosphate was recycled for further leaching of Valandai 1~.

With this technique, 90% of the soluble phosphate in balundite
I was able to collect more than η゛. Regarding the sodium that reacts to form notrium aluminate, about 20% of the sodium]-lium hydroxide was used, with more than 90% of it recovered in the form of sodium carbonate.

Example 2 In this experiment, a slurry of ground balundite, after grinding and leaching in two recycled sodium carbonate rams, was heated to boiling point to remove some of the carbon dioxide present as acidic sodium carbonate. The same technique as in Example 1 was used, except for the expulsion. By this method, the amount of sodium hydroxide used in the subsequent leaching is 90% of the stoichiometric amount.
decreased to

Example 3 In this experiment, potassium carbonate and potassium hydroxide were used in place of the sodium compound of Example 2. Due to the superior causticization rate of potassium salts, about 20% of the causticizable phosphates are solubilized during milling, leaving only stoichiometric amounts of potassium hydroxide used for subsequent leaching. The amount decreased to 85% of the theoretical amount. The overall effect was that there was no formation of by-product potassium carbonate and that the solution after aluminum hydroxide precipitation could be recycled directly to the milling.

It will be clearly understood that the invention in its general aspects is not limited to the specific details cited above.

13-

Claims (1)

[Claims] Medium: A method for producing an alkali metal phosphate from a substance containing phosphates of iron and aluminum, in which the substance is leached with a solution of ``alkali metal carbonate'' containing dissolved phosphates. 1- A method characterized in that a leachate is prepared and an alkali metal phosphate is collected from the leachate. (2) In a method for producing an alkali metal phosphate from a substance containing iron and aluminum phosphates, the substance is leached with an alkali metal charcoal W1mWI solution to dissolve the phosphate from the substance, and Leaching with alkali metal hydroxide, then dissolving phosphate from the substance, and collecting alkali metal phosphate from the leachate! ``!1''. (3) The method described in the middle section or (2) above, in which leaching is carried out at high concentration in an alkali metal carbonate solution. (4) An alkali metal The method according to item (3) above, wherein the leaching with a 1 m m solution is carried out under pressure at a temperature of 100° C. to 150° C. (5) Producing alkali metal phosphorus Flijl from naturally occurring apatite. In this method, the rock is leached with a hot solution of alkali metal carbonate to dissolve the phosphate from the rock, the alkali metal hydroxide is added, and the process is continued to further extract phosphate from the rock. A method characterized by dissolving residual solids from the leachate, and cooling the leachate to precipitate the phosphates. (6) Precipitating the phosphates from the solution. (5) carbonate to precipitate aluminum hydroxide and remove the precipitated aluminum hydroxide to produce an alkali metal carbon M salt solution that can be recycled to the first leaching step; ) The method described in item (7) The method described in item (5) or item (6) above, in which leaching is carried out in an alkali metal charcoal solution at a temperature of 4. (0) For alkali metals The leaching of the acid salt Wt is carried out under pressure from 100°C to 150°C.
The method described in section 7). (9) The method according to any one of the above items (5) to (8), wherein the alkali metal carbon i1 salt is I.lium carbonate. (I(D) The method according to any one of the above paragraphs (5) to (0), wherein the alkali metal carbon M1m is potassium carbonate. (Tll Contamination with a small amount of iron and aluminum phosphates) The resulting calcium phosphate rock is leached with a hot solution of sodium to lithium carbonate to lower the iron and aluminum phosphate content of the rock and to make the residual solids, mainly composed of calcium phosphate, suitable for conventional fertilizer production. The method according to item (1) above.